This invention pertains to a multiple bit screwdriver which can be actuated to withdraw a bit from the screwdriver""s chuck, return that bit to a revolver style magazine, select a different bit from the magazine, and feed the selected bit into the chuck.
The prior art has evolved a wide variety of multiple bit screwdrivers, some of which incorporate mechanisms for loading bits from a bit storage magazine directly into the screwdriver""s chuck and for removing bits from the chuck and returning them to the magazine. For example, U.S. Pat. No. 1,579,498 Anderson, issued Apr. 6, 1926 provides a screwdriver type tool in which the bit storage magazine comprises a plurality of chambers spaced radially around the inner circumference of the screwdriver""s handle. A cap on the end of the handle is rotated into alignment with a selected bit chamber. A xe2x80x9cplunger pinxe2x80x9d is then withdrawn through the cap, allowing the selected bit to drop into the space previously occupied by the plunger pin. The plunger pin is then pushed back through the cap, to force the selected bit through an apertured shaft which protrudes from the handle""s opposite end, until the tip of the bit extends through the bit chuck at the shaft""s outward end.
Anderson""s device has some disadvantages. For example, one must separately manipulate the cap and the plunger pin in order to select and load a bit. A further disadvantage is that Anderson""s device relies upon the force of gravity to move a bit from its storage chamber into the space evacuated by the plunger pin; or, to return a bit to an empty storage chamber. The force of gravity is also used to remove a bit from the chuck (i.e. the tool is held vertically and the plunger pin withdrawn, allowing the bit to fall out of the chuck and drop through the shaft into the space evacuated by the plunger pin). It is accordingly necessary for the user to orient and manipulate the tool between various horizontal and vertical positions in order to properly exploit the force of gravity as bits are loaded and unloaded. The present invention overcomes these disadvantages.
The invention provides, in one embodiment, a screwdriver having telescopically slidable inner and outer sleeves which form a bit storage member and a hand grip respectively. A plurality of bit storage cavities are formed around the inner circumference of the inner sleeve, such that a tool bit can be stored in each cavity. An apertured core extends longitudinally into the inner sleeve, and is coupled to a base portion which extends into and is slidably supported by the outer sleeve. An apertured shaft extends from the core""s forward end in coaxial alignment with the core""s aperture. The rearward end of a push rod is fastened to the outer sleeve""s rearward end, such that the push rod can be pushed longitudinally and coaxially through the inner sleeve, core and shaft. A magnet is supported on the push rod""s forward end. The core has a forwardly projecting and apertured stem in which a bit changing slot is provided. A magnetic lever arm is coupled to the core and biased toward the bit changing slot. The push rod is slidably movable through the core and inner sleeve between extended and retracted positions
When the push rod is in the extended position, the push rod magnet is located rearwardly of the bit storage cavities; the core can be rotated with respect to the inner sleeve to position the bit changing slot adjacent a selected bit storage cavity; and, the lever arm is pivotally biased toward and through the bit changing slot, magnetically attracting to the lever arm a tool bit located in the selected bit storage cavity. As the push rod is moved from the extended position into the retracted position, it initially pushes the lever arm and the magnetically attracted tool bit away from the selected bit storage cavity, through the bit changing slot and into the core. The push rod""s magnet is then pushed forwardly toward the rearward end of the tool bit, magnetically attracting the tool bit onto the push rod magnet. The push rod is then pushed through the core and shaft, pushing the tool bit forwardly through the core and shaft until the tool bit protrudes through the shaft""s open forward end.
During movement of the push rod from the retracted position into the extended position, the push rod magnet magnetically retains the tool bit on the forward end of the push rod as the push rod is pulled rearwardly, thereby pulling the magnetically attracted tool bit rearwardly through the shaft and the core""s stem to position the magnetically attracted tool bit adjacent the bit changing slot and the selected one of the bit storage cavities. A first spring is coupled between the lever arm and the core to bias the lever arm toward and through the bit changing slot. Movement of the push rod from the extended position into the retracted position pushes the forward end of the push rod against the lever arm, overcoming the first spring""s bias. Movement of the outer sleeve from the retracted position into the extended position withdraws the push rod from the lever arm, whereupon the first spring biases the lever arm toward and through the bit changing slot, sweeping the tool bit back into its bit storage cavity.
A first plurality of longitudinally extending ridges and grooves can be alternately interleaved on the inner sleeve""s outer surface. A second plurality of longitudinally extending ridges and grooves can be alternately interleaved on the outer sleeve""s inner surface. The first plurality ridges are sized and shaped for slidable longitudinal movement along the second plurality grooves; and, the second plurality ridges are sized and shaped for slidable longitudinal movement along the first plurality grooves. A third plurality of longitudinally extending ridges and grooves can be alternately interleaved on the base portion""s outer surface. The third plurality ridges are sized and shaped for slidable longitudinal movement along the second plurality grooves; and, the second plurality ridges are sized and shaped for slidable longitudinal movement along the third plurality grooves. The ridges and grooves are mutually aligned such that whenever the outer sleeve is telescopically slidably movable with respect to the inner sleeve, the bit changing slot is aligned with one of the bit storage cavities.